A solid hollow tube (thin wall) with pin in the bottom and the top part is connect with another tube and there is a force act on top of the tube ( tangent), the pipe has a small diameter (3feet) at both end and in the midle its has diameter of 6 feet. How to convert the uneven diameter of the hollow tube in to a solid tube (same stresst) ( keep the length the same)? what equation to use? moment of Inertia? and does it matter what kind of force act on the original hollow tube?